Digital differential analyzers



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DIGITAL DIFFERENTIAL ANALYZERS Filed Jan. 6, 1954 11 Sheets-Sheet 9 IN VEN TORS 6015472 z ifa( E ll mi Mw mgm Nov. 7, v1961 R.'M. BECK -Er AL DIGITAL DIFFERENTIAL ANALYzERs l1 Sheets-Sheet l0 Filed Jan. 6, 1954 2 HWK Nov. 7, 1961 Filed Jan. 6, 1954 R. M. BECK ET AL DIGITAL DIFFERENTIAL ANALYZERS 11 Sheets-Sheet 11 nite This invention relates to digital differential analyzers, and more particularly to an analyzer for utilizing decimal digits to facilitate its ease of operation.

lIn co-pending application, Serial No. 217,478, filed March 26, 1951, and now Patent No. 2,900,134, by Floyd G. Steele and William S. Collison, a digital differential analyzer is disclosed for Isolving complex differential problems by digital steps. The analyzer has the advantages of both digital computers and differential analyzers. The analyzer obtains the advantages of differential analyzers in that it is relatively simple in construction. The analyzer also has the advantage of digital computers in its speed and accuracy of operation. By combining these advantages, a computer is obtained which is able to solve complex differential equations even though it is housed in a cabinet smaller than a desk,

The digital differential analyzers now in use operate in the binary system to obtain the solution of digital problems. These systems have been entirely satisfactory from the standpoint of operation. However, operators of the machine have expressed some desire for an analyzer which will operate on a decimal basis. It has been the opinion of these people that a machine operating on a decimal basis can be initially coded relatively easily and that the results obtained during and after the solution of a problem can also be read and digested easily.

This invention provides a digital differential analyzer for converting binary information into decimal information and for solving differential problems on the basis of the decimal information. The analyzer operates on a decimal basis by combining bits of binary information into parallel combinations of signals such that each parallel combination represents a different decimal digit in a multi-digital number. The analyzer operates to simultaneously present the signals in each combination for computation. By utilizing parallel combinations of signals, not only the advantage of operating on a decimal basis but also the advantages of increased capacity and speed of operation are obtained.

An object of this invention is to provide a digital differential analyzer which operates in digital steps to obtain a solution of complex differential problems.

Another object is to provide an analyzer of the above character which is capable of being coded and of operating on a decimal basis to solve differential problems.

A further object is to provide an analyzer of the above character for converting binary bits of information into parallel combinations -of signals representing decimal digits and for utilizing the parallel combinations o-f signals to obtain speedy and accurate solutions of problems.

Still another object is to provide an analyzer of the above character which has a relatively large capacity for information and a relatively high speed of operation.

A still further object is to provide a method of solving differential problems in digital steps and on a decimal basis.

Other objects and advantages will be apparent from a detailed description of the information and from the appended drawings and claims.

3,097,640 Patented Nov. 7, 1961 In the drawings:

FIGURE 1 is a simplified block diagram which schematically illustrates a digital differential analyzer forming one embodiment of this invention; v

FIGURES 2, 3, 4, 5 and 6 are schematic diagrams, partly in block form and partly in perspective, illustrating in some detail an operating system of the digital differential analyzer shown in FIGURE 1;

FIGURE 7 is a block diagram illustrating the operation of one of the integrators forming part of the digital differential analyzer shown in FIGURES 2 to 6, inclusive;

FIGURE 8 is a curve illustrating the operation of an integrator such as the integrator shown in FIGURE 7;

FIGURE 9 is a chart which illustrates how different parts of an integrator such as that shown in FIGURE 7 are coded to control the operation of the integrator;

FIGURE 10 is a schematic diagram illustrating the relationship between different integrators forming the digital differential analyzer shown in FIGURES 2 to 6, inclusive, when the analyzer is solving a particular problem;

FIGURE 11 is a chait illustrating the operation of certain of the components forming a part of the analyzer shown in FIGURE 1 and in FIGURES 2 to 6, inclusive;

FIGURE 12 is a chart which illustrates the operation of certain of the components shown in FIGURES 2 to 6, inclusive;

FIGURE 13 is a chart illustrating the operation of certain of the components in analyzers now in use to provide a comparison with the chart shown in FIG- URE 12.

FIGURE 14 is a chart which illustrates the operation of certain of the components shown in FIGURES 2 to 6, inclusive; and

FIGURE 15 is a diagram of a fiip-op unit which forms a basic stage of the analyzer shown in FIGURE 1 and of the analyzer shown in FIGURES 2 to 6, inclusive.

A simplified operation-illustrating block diagram is shown in FIGURE 1 of an analyzer for solving differential problems by digital steps. The analyzer includes a drum (similar to drum 10 schematically shown in FIGURES 2 to 6, inclusive) adapted to be rotated by a suitable motor (not shown). A thin coating 12 (FIG- URE 2) of magnetic material is applied to the periphery of the drum. The coating 12 can be considered as being divided into a plurality of annular channels 14, 16, 1S, 20, 22, 24 and 26. These channels are shown schematically in FIGURE 1 in separated relationship for purposes of convenience. Each of the channels is separated by a sufficient distance from its adjacent channel so as to be substantially unaffected by the magnetic information provided in the adjacent channel.

The circumferential distance of each channel may be considered as being divided into a plurality of positions. Each of the positions is sufficiently separated from its adjacent positions to receive a different magnetization than that provided on the adjacent positions. For eX- ample, approximately 116()I equally spaced pulse positions may be provided in each channel when the drum has a radius of approximately four inches.

A plurality of toroidal coils are positioned adjacent to each of the channels 14, 16, 18, 20, 22, 24 and 26. For example, coils 27, 28 and 30 are provided in contiguous relationship to the channel 14. These coils are shown schematically in FIGURE 1. Similarly, coils 32, 34 and 36; coils 38, 4t) and 42; coils 44, 46 and 48; coils Sti, 52 and 54; and coils 56, 58 and 60 are `associated with the channels 16, 1S, 20, 22 and 24, respectively. A single coil 62 is disposed .adjacent the channel 26.

The coils 27 and 30 are effectively separated from each other by approximately 104 pulse positions, and the coil 28 is disposed at an intermediate position between the coils 27 and 30. The coil 30 is adapted to provide signals in a pattern dependent on the operation of the digital differential analyzer and to induce the corresponding magnetic pattern on :the drum as the drum rotates. The pattern induced on the drum 10 by the coil 30 is of the binary form in which a magnetization in one circumferential direction indicates one value and a magnetization in the other direction indicates a second value.

The coil 27 is adapted 'to pick up the changes in the direction of magnetization in the channel 14 as the drum rotates. The coil 28 is adapted to produce a substantially constant signal for returning the direction of magnetization on the drum to that representing a value of 0 after the magnetic pattern on the drum has been converted into a corresponding electrical pattern by the coil 27.

The coils 32, 34 and 36 are separated from one another by distances corresponding to the distances between the coils 27, 28 and 30 and are adapted to perform functions similar to those performed by the coils 27, 28 and 30, respectively. The coils 38, 40 yand 42 and the coils 44, 46 and 48 are also separated in the channels 18 and 20 in a similar manner to the separation of the coils in the channel 14 and are adapted to perform functions corresponding to those performed by the coils 27, 28 and 30, respectively.

The coils 52 and 58 are `adapted to operate in a manner similar to the coil 30 to provide a magnetic pattern in the channels 22 and 24, respectively, in a pattern dependent upon the problem to be solved. The coils 52 `and 58 are effectively separated from the coils 54 and 60, respectively, by approximately 49 pulse positions during the operation of the analyzer to obtain the solution of a mathematical problem.

The coils 54 and 60 are adapted to produce signals in accordance with the magnetic pattern provided in their respective channels by the coils 52 and 58. The coils 50 and 56 are adapted to operate in a manner similar to the coil 28 to produce a zero direction of magnetization in the channels 22 and 24, respectively, after the patterns provided by the coils 52 and 58 have been utilized by the coils 54 and 60, respectively.

The coil 62 is adapted to produce a cycle of a signal approximating a sine wave as each pulse position in the channel 26 moves past the coil. The coil 62 produces sinusoidal signals because of the magnetic pattern permanently provided in the channel 26. This pattern remains constant regardless of the problem to be solved.

A counter 66 is connected to the coil 62 to count the cycles of the sine waves in the channel 26 as the drum rotates. The counter 66 is formed from a plurality of multivibrators connected in cascade arrangement and is adapted to count successive sine signals in a numerical range from l to 48. Upon each count of 48, the counter 66 is adapted to return to its initial state for the commencement of a new count. As will be disclosed in detail hereinafter, a new integrator i.e. integrator storage section is presented for computation upon the completion of each count of 48.

Similarly, a counter 67 is formed from a plurality of multivibrators in cascade arrangement. The counter 67 is connected to the counter 66 to count the number of times that a full count is obtained in the counter 66. For example, the counter 67 may count up to 22 full counts in the counter 66 before returning to its initial state for the initiation of `a new count. In this way, the counters 66 and `67 divide the drum 10 into 22 integrators each having 48 pulse positions.

As schematically shown in FIGURE 1, the output signals induced in the coil 32 are introduced to a gate circuit 68, which also has signals applied to it through a line 70 from the counter 66. The output signals from the gate circuit 68 are in turn applied through an or network 72 to the coil 36. Similarly, a gate circuit 74 receives signals from the coil 38 and through the line 70 from the counter 66. The output terminal of the gate circuit 74 is connected to an input terminal of an or network 76 having its output terminal connected to the coil 42.

The coil 32 is not only connected to the gate circuit 68 lbut also to an input terminal of a gate circuit 78 having other input terminals connected to the coils 54 and 60 and through the line 70 to the counter 66. The output from the gate circuit 78 passes to a counter 80 formed from a plurality of multivibrators in cascade arrangement. The output from the counter 80 is in turn applied to input terminals of gate circuits 82, 84, 86 and 88 having other input terminals connected to the plate of the left tube in a multivibrator 90. The output terminals of the gate circuits 82, 84, 86 and 88 are connected to input terminals of an adder 92. The adder 92 comprises a system for additively combining various quantities represented by electrical signals in a manner to be explained. The structure of the adder `92 is not given since the system of FIGURE 1 is merely a simplified illustrative system, 1and the structure of an operating system will be subsequently described in detail.

The signals from the coil 32 are also introduced to an input terminal of a gate circuit 94 having another input terminal connected through a line 96 to the counter 66. The output from the gate circuit 94 is applied to the grid of the left tube in a bistable multivibrator 98, the grid of the right tube in the multivibrator being connected through a line 100 to the counter 66. The plate of the left tube in the multivibrator 98 is connected to an input terminal of a gate circuit 104, another input terminal of which is connected to the coil 62. The signals passing through the gate circuit 104 are introduced directly to the grid of the left tube in the multivibrator and through an or network 106 to the grid of the right tube in the multivibrator to change the state of the multivibrator 90 with each signal. Signals also pass from the counter 66 through the line 100 and the or network 106 to the grid of the right tube in the multivibrator 90.

In addition to receiving the signals from the gate circuits 82, 84, 86 and 88, the adder 92 also receives signals from the coils 27, 32, 38 and 44. The signals from the gate circuits 82, 84, 86 and 88 are arithmetically combined with the signals from the coils 27, 32, 3S and 44. The results obtained are applied directly to the coil 30, through the or network 72 to the coil 36, through the or network 76 to the coil 42, and directly to the coil 48.

The pulses induced in the coils 27, 32, 38 and 44 are also applied to input terminals of gate circuits 110, 112, 114, and 116, respectively. Connections are also made to input terminals of the gate circuits 110, 112, 114 and 116 from the plate of the left tube in the multivibrator 90 and from the plate of the left tube in a multivibrator 117. Connections are respectively made to the grids of the left and right tubes in the multivibrator 117 from a gate circuit 118 and through the line 100 from the counter 66. The gate circuit 118 in turn receives signals from the coils 38 and S4 and through the line 70 from the counter 66.

The output signals from the gate circuits 110, 112, 114 and 116 are introduced through suitable delay lines 119, 120, 121 and 122, respectively, to the adder 92 for combination with the signals from the coils 27, 32, 38 and 44. The delay lines 119, 120, 121 and 122 may be bistable multivibrators to delay by one pulse position the information from the gate circuits 110, 112, 114 and 116. The output signals obtained by the adder 92 are applied to the coils 30, 36, 42 and 48.

The output signals passing from the adder 92 to the coil 48 are also applied to gate circuits 123 and 124 having other input terminals connected through the line to the counter 66. The output signals from the gate circuits 123 and 124 respectively pass through or networks 125 and 126 for introduction to the coils 52 and 58. The or networks 125 and 126 also respectively receive signals from gate circuits 128 and 131i. Connecltions are made to input terminals of the gate circuit 123 from the coil 54 and through a line 132 from the counter 66. Similarly, input terminals of the gate circuit 13%l are connected to the coil 60 and the line 132.

The digital differential analyzer as illustratively described above in simplified form is adapted to provide the solution of differential equations. For example, it may provide the solution of the problem of evaluating the integral of a general equation y=f(x) so as to obtain a function fydx=ff(x)dx, Where f(x) represents a function of x and ff(x)dx represents the integral of the function. If a curve y=f(x) is plotted with x as the abscissa and y as the ordinate, the analyzer obtains the relationship fydx=ff(x) dx by computing the area under the curve y==f(x). By determining the area under the curve y=;f(x), the analyzer performs electronically operations that may sometimes be performed mentally by a skilled mathematician when the problem to be solved is relatively simple.

The analyzer obtains the value of the function by producing small increments of x. These increments may be represented by the symbol Ax. For each Ax increment, the analyzer determines the value of y and obtains the product yAx. This product yAx approximates the area under the curve y=f(x) for each Ax increment, as indicated in FIGURE 8 by the shaded area 140` for a particular Ax increment. If the product yAx is obtained for successive Ax increments and if all of the yAx increments are added together, the area under the interval of the curve representing f(x) from x to x may be approximated. A relatively accurate approximation may be obtained by decreasing the value of each Ax increment.

An integrator for determining the yAx increments and for storing the cumulative values of these increments is shown in 'FIGURE 7. The integrator includes a transfer stage 142 for obtaining Ax increments at periodic intervals through a line 144. The integrator also has an integrand accumulator 146 for storing the value of the dependent quantity y and for receiving Ay increments through a line 14S from its own and from other intergra tors so as to vary the value of y in accordance with the function y=f(x). An output accumulator 15G` is provided to receive yAx increments, to combine each yAx increment with the previous increments and to deliver the cumulative value obtained to another integral accumulator or transfer stage while holding the remainder in store. A detailed explanation of this will be given hereafter.

The interrelationship between different integrators is illustrated in FIGURE l0 for a particular problem. ri his problem starts with a differential equation represented by As is mathematically known, the differential solution of this problem indicates that y=tan x. The interrelationship illustrated in FIGURE l0 utilizes this solution to generate the function tan x which is accumulated in the register of an output integrator. The integrators involved in the generation of the function tan x are indicated in FIGURE l0v by blocks 152, 154, 155, 158 and 16). In each integrator, the introduction of the Ax increments constituting changes in the independent variable quantity for the integrator is indicated by a line extending into the upper right position in the block. The Ay increments are introduced into the integrator through a line or a plurality of lines extending into the lower right portion of the block representing the integrator. The output of the integrator is obtained from a line extending from an intermediate position at the right side of the appropriate block.

As will be seen in FIGURE l0, Ax increments of the independent variable for a particular integrator may Vbe obtained from the output of another integrator. For example, in FIGURE l0, the Ax increments for the integrators 154 and 156 are obtained from the output of the integrator 152. Similarly, Ay increments for a particular integrator may be obtained from the output of other integrators as well as from the output of the integrator itself. For example, Ay increments for the integrators 154 and 15S are obtained from the output of the integrator 152.

The Ay and Ax increments for each integrator are actually determined from a coded pattern provided in the channels 1li; and 18, respectively. As previously disclosed, the pulse positions in each channel are subdivided into 22 integrators each having 48 pulse positions, The first 22 positions in each integrator in the channel 1? are coded to indicate a Ax increment. Since the rst 22 positions in the channel 1S for each integrator correspond in number to the 22 integrators in the analyzer, each integrator can receive a Ax increment from the output of any of the other integrators. This can be effectuated by providing a pulse in the channel 18 in a particular one of the first 22 positions for the integrator.

For example, the Ax increments for the integrator 154 in FIGURE l0 would be coded in a particular one of the 22 positions in the channel 18. As will be disclosed in detail hereinafter, the particular position corresponds to the time at which the output from the integrator 152 appears on the coils 54- and Gil. In FIGURE 9, a pulse 162 is shown as being recorded in the channel 18 in the 11th pulse position for a particular integrator.

A pulse in the channel 18 in one of the first 22 positions for a particular integrator indicates that a Ax increment may be made for the integrator. However, such a pulse does not indicate whether an increment will actually be made and, if so, whether the polarity of such increment will be positive or negative. The actual occurrence of a Ax increment for the integrator is indicated by the presence or absence of a coincidental pulse in the channel 22. If a positive pulse is picked up from the channel 22 by the coil 54- at the same time as the pulse representing a possible Ax increment for a particular integrator is picked up by the coil 33, a Ax increment for the integrator actually occurs. For example, the pulse 162 in FIGURE l0 indicates an actual Ax increment for a particular integrator since it coincides in time with a pulse 164 in the channel 22. A Ax increment is not obtained for the integrator if a pulse does not appear in the channel 22 at the same time as the pulse in the channel 18.

The polarity of each Ax increment is determined by the presence or absence of a coincidental pulse in the channel 24. It' a pulse is picked up from the channel 24 yby the coil 6u at the same time that pulses indicating an actual Ax increment for a particular integrator are picked up by the coils 38 and 54, the Ax increment for the integrator is positive. The Ax increment is negative if a pulse does not appear in the channel 24 at the same time as the pulses in the channels 18 and 22. For example, the pulse 162 in FIGURE 9 indicates a negative Ax increment since a pulse does not appear in the channel 24 simultaneously with the occurrence of the pulses 1162 and 164 in the channels 18 and 22, respectively.

The first 22 positions in the channel 16 for each integrator `are coded to indicate Ay increments in a manner similar to the coding of corresponding positions in the channel 1S to indicate Ax increments. Since the first 22 positions in each integrator correspond to the 22 integrators in the digital differential analyzer, each integrator is coded in particular ones of the rst 22 positions in the channel 16 so as to receive the outputs from certain other integrators in accordance with the problem to be solved. For example, a pulse would be coded in the channel 16 in a particular one of the first 22 positions for the integrator 158 in FIGURE 10 so as to coincide with the time at which the output from the integrator 152 is made available to the coils 54 and y60 in the channels 22 and 24, respectively. Although only one Ax increment can be obtained for an integrator upon each revolution of the drum, several Ay increments can be obtained. This may be seen by the pulses 168 and 170 in the channel 16 in FIGURE 9.

Each pulse in the first 22 positions in the channel 16 for each integrator represents the possibility of a Ay increment but does not indicate the actual occurrence of such an increment or the polarity of the increment. The actual occurrence of the increment is indicated by the presence or absence of a pulse in the channel 22 at the same time that the pulse in the channel'16 is made available to the coil 32. For example, the pulse 168 in FIGURE 9 indicates an actual Ay increment for a particular integrator since it coincides in time with a pulse 172 in the channel 22. However, no Ay increment is obtained when the pulse 170 is picked up by the coil 32 since there is no coincidental pulse in the channel 22.

The sign of each actual Ay increment is indicated by the presence or absence of a pulse in the channel 24 at the time that pulses in the channels 16 and 22 are simultaneously made available to the coils 32 and 54. For example, the pulse 168 in FIGURE 9 indicates a positive Ay increment for a particular integrator since a pulse 174 appears in the channel 24 at the time that the pulses 168 and 172 are picked up by the coils 32 and 54, respectively.

Since the interrelationship between the different integrators remains constant during the solution of a particular problem, the coding pulses in the channels 16 and 18 for the first 12 positions of the integrator must be retained during the computation. Retention of the pulses in the channel 16 is efiectuated by the gate circuit 68, which remains open during the first 22 positions in each integrator to pass the coded information in these positions. The gate circuit 68 opens during these pulse positions because of the introduction of a relatively high voltage through the line 70 from the counter 66. The signals then pass through the or network 72 for recordation by the coil 36 in the channel 16. Similarly, the gate circuit 74 opens during the first 22 positions for each integrator so that the coding information can pass through the or network 76 for recordation by the coil 42 in the channel 18.

It should be appreciated that the gate circuits similar to the circuit 68 operate to pass information only when positive pulses are simultaneously introduced to all of the input terminals of the circuit. In computer terminology such circuits have been designated as and networks. The term or networks is also common in computor terminology. Such circuits o-perate to pass such information when any one of their input terminals receives a relatively high voltage. Such or networks are shown in the drawings as triangles and are exemplified by the networks 72 and 76.

During the first 22 positions of each integrator, the gate circuit 78 operates to determine the occurrence of Ay increments for the integrator and the polarity of each such increment. The gate circuit 78 makes such determinations by comparing the pulses from the coil 32 with the pulses from the coils 54 and 60. Each pulse induced in the coil 32 in the first 22 positions for an integrator indicates that a Ay increment can be obtained. As previously disclosed, the particular position in which a pulse occurs determines for an integrator which of the other integrators in the analyzer provides Ay increments for the integrator. The simultaneous production of a pulse by the coil 54 indicates that a Ay increment has actually occurred. When the coil 60 also produces a simultaneous pulse, the gate circuit 78 indicates that the Ay increment has a positive polarity.

At the same time that the gate circuit 78 operates to determine the occurrence of Ay increments for an integrator and the polarity of each such increment, the counter 80 arithmetically combines each such Ay increment. For example, a signal passing to the counter 80 from the gate circuit 78 may cause the circuit to provide a numerical indication of +4 when an indication of +3 was previously provided by the counter. Similarly, the indications in the counter 80 may change from a value of -3 to a value of -4 upon the introduction of a negative signal from the gate circuit 78.

The counter 80 retains in binary form the numerical information relating to the cumulative value of the Ay increments for an integrator. The counter 80 retains the information in binary form since it comprises a plurality of multivibrators arranged in cascade relationship. In this embodiment, four multivibrators in cascade arrangement are provided. For example, with a resultant count of |5 for the Ay increments for a particular integrator, the first and third multivibrators in the cascade arrangement may be operated to indicate a binary pattern of 0101, where the least signicant digit is at the right. In binary form, a pattern of 0101 indicates that (0)(23)-I-(1)(22H-(0)(21)+(1)(2)=5 Similarly, a value of -l-S is indicated by a pattern of 0011, Where the least significant digit is at the right.

As previously disclosed, the information controlling increments in the dependent quantity for each integrator is provided in the channel 16 in the first 22 pulse positions for each integrator. The information relating to the dependent quantity y itself occurs in the channels 14, 16, 1S and 20 after the 22nd pulse position for each integrator. As will be disclosed in detail hereinafter, a group of pulse indications simultaneously appearing in the channels 14, 16, 18 and 20 provides an indication as to the value of a decimal digit.

The information relating to the dependent quantity y for each integrator is preceded by a pulse in the channel 16 to indicate that the information which follows relates to the dependent quantity y. For example, a pulse may occur in pulse position 28 for an integrator to indicate that the subsequent information in the channels 14, 16, 18 and 20 relates in part to the dependent quantity y for the integrator. This pulse has been designated in co-pending application Serial No. 217,478 as the start pulse.

The start pulse in the channel 16 is introduced to the gate circuit 94, which also receives signals through the line 96 from the counter 66. Since a relatively high voltage appears on the line 96 only after the 22nd pulse position for each integrator, the start pulse is the first pulse which is able to pass through the gate circuit 94. This pulse passes to the grid of the left tube in the multivibrator 98 and cuts off the tube. The resultant relatively high Voltage on the plate of the left tube in the multivibrator 98 is introduced to the gate circuit 104.

Because of its connection to the coil 62, the gate circuit 104 passes each clock signal in the channel 26 after a relatively high voltage is introduced to it from the multivibrator 98. The signals from the gate circuit 104 are introduced directly to the grid of the left tube in the multivibrator and through the or network 106 to the grid of the right tube in the multivibrator. The iirst signal from the -gate circuit 104 causes the left tube in the multivibrator 90 to become cut off for reasons which will be disclosed in detail hereafter. Upon the passage of a second signal through the gate circuit 104, the grid of the right tube in the multivibrator 90 becomes cut off and the left tube starts to conduct.

Similarly, the left tube in the multivibrator 90 becomes alternately cut off upon the introduction of odd signals from the gate circuit 104 and the right multivibrator tube becomes cut off upon the introduction of even signals. At the 48th pulse position for each integrator, a signal is introduced from the counter 66 through the line 100 and the or network 106 to the grid of the right tube of the multivibrator 90 so as to cut off the tube. In this way, the multivibrator 90 is prepared to have its left tube cut olf upon the passage of the rst signal through the gate circuit 104 for the next integrator.

As previously disclosed, the plate of the left tube in the multivibrator 90 becomes cut off upon the passage of the first signal through the gate circuit 104. When the left tube in the multivibrator 90 becomes cut off, a relatively high voltage is introduced from the plate of the tube to the gate circuits 82, 84, 86'and 88 to open the gate circuits for the introduction of information from the counter 80. information relating to the least significant binary unit is introduced from the counter 80 to the gate circuit 82 and information relating to binary digits or increasing significance are simultaneously introduced to the gate circuits 84, 86, 88. It has already been disclosed that the information introduced to the gate circuits from the counter 80 relates to increments in the dependent quantity y for each integrator.

The information from the counter 80 passes through the gate circuits 82, 84, 86 and 88 to ,the adder 92 for combination with the signals induced in the coils 27, 32, 38 and 44, respectively at alternate pulse positions, when the signals induced in the coils 27, 32, 38 and 44 relate to the dependent quantity y for the integrator undergoing computation. For example, when the start pulse for an integrator occurs at pulse position 27 for the integrator', pulse position 28 constitutes the first information pulse. Information relating to the value of the dependent quantity y for the integrator is accordingly provided in the channels 14, 16, 18 and 20 in pulse position 28 for the integrator and subsequently in alternate pulse positions such as pulse positions 30, 32, 34 etc.

The information relating to the dependent quantity y for each integrator is provided in the channels 14, 16, 18 and 20 on a decimal basis. For example, when the start pulse occurs in pulse position 27, the information in the channels 14, 16, 18, and 20 for pulse position 28 provides an indication of a decimal number between and 9 inclusive. Similarly, the information in the channels 14, 16, 18 and 20 for pulse position 30 provides an indication of the tens digit such as 10, "20, "30 etc. The exact manner in which the signals in the channels 14, 16, 18 and 20 provide such decimal information will be disclosed in detail hereafter.

Since the information in the channels 14, 16, 18 and 20 relate to decimal indications in a particular decimal code and since the signals passing through the gate circuits 82, 84, y86 and 88 relate to` binary information, the signals passing through the gate circuits 82, 84, 86 and 88 are rst converted to a decimal basis of the particular code before they are combined with the signals induced in the coils 27, l32, 38 and 44. The correction required to produce this conversion to a decimal base and the circuitry required for such conversion will be described in detail subsequently in connection with the detailed system shown in FIGURES 2 to 6 inclusive. The resultant signals produced by the adder 92 provide an indication in decimal form of the new value of the dependent quantity for the integrator undergoing computation. These signals are introduced to the coils 30, 36, 42 and 43 for recordation in the channels 14, 16, 18 and 20, respectively.

The pulses induced in the coils 27, 32, 38 and 44 are not only introduced to the adder 92 but also to gate circuits 110, 112, 114 and 116, respectively. Since the gate circuits 110, 112, 114 and 116 are also connected to the plate of the left tube in the multibrator 90, the gate circuits become prepared for opening at alternate pulse positions after the start pulse. In these pulse positions, in-

formation relating to the dependent quantity y for each integrator is presented in the channels 14, 16, 18 and 20.

The gate circuits 110, 112, 114 and 116 become opened for the passage of information to the adder 92 only when a relatively high voltage is introduced to them from the plate of the left tube in the multivibrator 117. Such a high voltage is produced on the plate of the left tube in the multivibrator 117 when a signal passes to the grid of the tube from the gate circuit 118 and since the gate circuit is connected through the line 70 to the counter 66, it is prepared for opening only during the first 22 pulse positions of each integrator. During these pulse positions, a signal passes through the gate circuit 118 when pulses of relatively high voltage are simultaneously induced in the coils 38 and 54. The pulse of relatively high voltage induced in the coil 38 indicates the possibility of a Ax increment for an integrator undergoing computation. When a pulse simultaneously is induced in the coil 54, an indication is provided that a Ax increment has actually occurred for the integrator.

Since the signal passing through the gate circuit 118 provides an indication that a Ax increment has actually occurred for an integrator', the voltage on the plate of the left tube in the multivibrator 117 becomes relatively high only upon the actual occurrence of such an increment. When the voltage on the plate of the left tube in the multivibrator 117 becomes high, it remains high during the time that the remaining pulse positions in the integrator are presented for computation. At pulse position 48 for the integrator, a signal is introduced to the grid of the right tube in the multivibrator 117 through the line 100 from the counter 66 so as to cut off the right tube in the multivibrator and make the left tube conductive. In this way, the left tube in the multivibrator 117 is prepared to become triggered into a state of non-conductivity upon the occurrence of a Ax increment for the next integrator.

Because of the connection between the plate of the left tube in the multivibrator 117 and the gate circuits 110, 112, 114 and 116, information is able to pass through the gate circuits only when a Ax increment has actually occurred for an integrator. As previously disclosed, this information relates to the new value of the dependent quantity y for the integrator. The information in the channels 14, 16, 18 and 20 relating to the value of the dependent quantity y for an integrator is delayed by one pulse position and is then differentially combined in the adder 92 with the signals in the channels 14, 16, 18 and 20 relating to the cumulative value of the differential combination yAx for the integrator. The new information relating to the cumulative value of the differential combination for each integrator is recorded in alternate pulses positions in the channels 14, 16, 18 and 20.

Sometimes, as the yAx increments for an integrator are added to the cumulative 'value of the differential combination for the integrator, an over-now is obtained in the information stored in the channels 14, 16, 18 and 20. When an over-ow occurs in the cumulative value of the differential combination for an integrator, the indications representing the cumulative value return to an intermediate value so that they can build up again to a relatively high value. At the same time, an overiiow pulse is produced by the adder 92 at pulse position 48 for the integrator. This pulse passes through the gate circuit 123 since the gate circuit opens at the last pulse position for each integrator because of its con- .nection through the line to the counter 66. The pulse then passes through the or network 125V for recordaton by the coil 52 in the channel 22.

For example, a iirst pulse of relatively high voltage may be provided in the channel 22 at the 48th position of integrator 1. This pulse indicates that an overflow has occurred in the cumulative yAx value stored in the channel 18 for the integrator but the pulse does not indicate whether the overflow is positive or negative. The

11 pulse is indicated at 180 in the chart shown at FIG- URE. 11.

In all of the vertical columns in the chart shown in FIGURE 1l, except for the two at the extreme right, numbers between l and 22 are shown corresponding to the 22 integrators in the digital diiferential analyzer. In the two columns at the extreme right, numbers are shown prefaced by the letters I and P. The letter I followed by a number indicates the particular integrator that is moving past the coil 52 at any instant. For example, I3 indicates that a pulse position in the third integrator is moving past the coil 52 in the channel 22. Similarly, a designation such as P13 indicates that the 13th pulse position in the particular integrator is moving past the coil S2.

After the pulse 181i is recorded by the coil 52 in the channel 22, it advances from the coil 52 towards the coil 54. During this time, the first 47 positions of integrator 2 are passing under the coil 52. At the P4812 position-or, in other words, the last position of integrator 2-an indication is recorded by the coil 52 in the channel 22, as indicated at 182 in FIGURE 1l. At the P1I3 position, the indication 180 passes through the gate circuit 128 and the or network 124 to the coil 52. The pulse passes through the gate circuit 128 since the gate circuit opens in the first 47 pulse positions of each integrator. After passing through the gate circuit 128 and the or network 125, the pulse 13S is again recorded by the coil 52 in the channel 22, this time at the pulse position adjacent to the indication 182.

Similarly, indications are provided in adjacent pulse positions to show whether or not an over-flow has occurred in the cumulative yAx 'value for each of the other integrators in the analyzer. These indications are recirculated by the gate circuit 128, which remains open during the rst 47 pulse positions of each integrator. At the 48th position for each integrator, the gate circuit 12S closes and prevents any recirculation of old information for the integrator.

At the same time that the gate circuit 123 closes, the gate circuit 123 opens. When the gate circuit 123 opens, the overflow information for the integrator moving past the coil 52 is recorded in the channel 22. In this way, old over-flow information for an integrator is replaced by new over-ow information for the integrator every time that the integrator is presented for computation.

After the indications have been provided in the channel 22 for the 48th pulse position of each integrator, integrator l is presented for computation a second time. As the drum lili rotates through the first 22 positions for the integrator, the output indications for the 22 integrators move in sequence past the coil 54. This causes the ouput indications in the channel 22 to become available for determining whether or not a Ax increment and Ay increments are actually obtained for the integrator during the second computation. The determination of the occurence of an actual Ax increment and of actual Ay increments is made by respectively comparing the coding pulses in the channels 16 and 1S with the overiiow pulses in the channel 22. The operation of the digital diiferential analyzer to obtain such a determination has been disclosed previously.

In FIGURE l, several bi-stable multivibrators, such as the multivibrator 90, are shown. Furthermore, the construction and operation of these multivibrators have been disclosed above on a general basis. A specific circuit for use as such multivibrators is shown in FIGURE l5. The multivibrator includes a pair of tubes 560 and 5412. The grid of each tube is connected to an appropriate output stage. For example, if the circuit shown in FIGURE l serves as the multivibrator 90 in FIG- URE 1, the grid of the tube 500 would be connected to the output terminal of the gate circuit 104 and the grid of the tube 502 would be connected to the output terminal of the or network 106. The cathodes of the 12 tubes are connected to the coil 62 and to a suitable source of positive biasing voltage.

Connections are respectively made from the plates of the tubes 50% and S02 through suitable coupling capacitances to the grids of tubes 504 and 566. The cathodes of the tubes 594 and 566 are both connected through a suitable resistance and capacitance to a source of negative Voltage. The plate of the tube 504 is coupled to the grid of the tube 5G16 by a suitable resistance 508 and capacitance 511i connected in parallel. Similarly, the plate of the tube 5% is coupled to the grid of the tube S94 through a resistance 512 and a capacitance 514 connected in parallel.

The plate of the tube 504 is also connected to one terminal of a resistance 516, the other terminal of which is connected to an output line 518. Connections are made from the output line 518 to the cathode of a diode 5211 and to the plate of a diode 522. The plate of the diode 523 biased at approximately -25 v. and the cathode of the diode 522 is biased at approximately 0 v. The plate of the diode 520 and the cathode of the diode 522 also have common terminals with the plate of a diode 524 and the cathode of a diode 526, respectively. The cathode of the diode 524 and the plate of the diode 526 are connected to'an output line 528 and to one terminal of a resistance 53) having its other terminal connected to the plate of the tube 5116.

Clock pulses are introduced to the cathodes of the tubes Sti@ and 502 from the coil 62 to reduce the voltages on these tubes from a positive voltage to approximately 0 volt. Upon the simultaneous introduction of a positive pulse to the grid of one of the tubes, the tube conducts. For example, the tube 511? conducts when a positive pulse of voltage is introduced to it from the gate circuit 104. When the tube Sti@ conducts, the voltage on the plate of the tube falls and causes the tube S64 lto become cut off. Since the tube 5114 is no longer conductive, the voltage on the plate of this tube rises. This voltage is `introduced through the resistance 508 and capaci-tance 51) to the grid of the tube 506 to make the tube 506 conductive.

Similarly, the tube 506 becomes conductive when a pulse is introduced to the grid of the tube from `the or network 106 at the same time that a clock pulse is introduced to the cathode of the tube from the coil 62. This causes the tube 536 to become cut off and a relatively high voltage to be produced on the plate of the tube. Upon the production of this high voltage, the tube 504- starts to conduct. In this way, either the tube S04 or the tube 596 conducts at any one time and the other tube is cut ott.

The diodes 526, S22, 524 and 526 serve as a clamping network to maintain the voltages on the output lines 518 and 523 at either 0 volt or -25 volts. For example, when a potential of -25 volts is to be produced at the output line 518, current flows through the diode 52) to maintain this potential in case of any tendency of the voltage to become more negative than -25 volts. Similarly, the diode 522 passes a current when a potential of O volt is to be produced at the output line 51S and the potential on the line tends to rise above 0 volt.

An operative embodiment of the system illustratively shown in FIGURE 1 and disclosed above is shown in some detail in FIGURES 2 through 6, inclusive. The system includes the channels 14, 16, 18, 20, 22, 24 and 26 and the coils respectively associated with the different channels. For example, the coils 27, 2S and 30 are associated with the channel 14. The coil 27 is connected to the grid of the left tube in a bistable multivibrator 202 (FIGURE 2) and to the input terminal of an inventer 204, the output from which is introduced to the grid of the right tube in the multivibrator 202. In like manner, a multivibrator 206 and an inverter 208; a multivibrator 210 and an inverter 212; a multivibrator 214 and an inverter 216; a multivibrator 218 and an inverter 220; and

spot/,cao

a multivibrator 222 and an inverter 224 are respectively associated with the coils 32, 38, 44, 54 and 68.

Connections are made from the plates of the left and right tubes in the multivibrator 286 to input terminals of gate circuits 228 and 230, respectively. Other input terminals of the gate circuits 228 and 23) are connected through a line 232 to a counter 234 corresponding to the counter 66 shown in FIGURE 1. Similarly, the voltages on the plates of the left and right tubes in the multivibrator 210 are respectively introduced to input terminals of gate circuits 236 and 238 having other input terminals connected through the line 232 to the counter 234.

The output signals from the gate circu-its 228 `and 238` respectively pass through or networks 248 and 242 to the grids of the left and right tubes in a bistable multivibrator 244. The voltage on the plate of the left tube in the multivibrator 244 is in turn introduced through an or network 245 to the coil 36 for recordation in the channel 16. In like manner, the signals from the gate circuits 236 and 238 respectively pass through or networks 246 and 248 to the grids of the left and right tubes in a bistable multivibrator 250. A connection is made from the plate of the left tube in the multivibrator 250` to the coil 42 tor the recordation of information in the channel 18. It shall be understood that the bistable multivibrators 244 and 250 each contain circuitry for creating a delay of one pulse position.

The voltage on the plate of the left tube in the multivibrator 206 is not only introduced to the gate circuit 228 but also to a gate circuit 254 having other input terminals connected to the line 232 and to the plate of the left tube in the multivibrator 218. The output signals from the gate circuit 254 pass to input terminals of gate circuits 256 and 258, other input terminals of which are respectively connected to the plates of the left and right tubes in the multivibrator 222. The output terminals of the gate circuit 256 and 258 are connected to a counter 268 corresponding to the counter 86 shown in FIGURE l for summing the Ay elements of the dependent variable.

The output terminals of the counter 268 are connected to input terminals of gate circuits such as circuits 262, 264, 266 and 268 having other input terminals connected through a line 270 to the counter 234. Only certain of the gate circuits are shown in FIGURE 2 for purposes of simplicity. The output terminals of the gate circuits such as the circuits 262, 264, 266 and 268 are in turn connected to the grids of the left and right tubes in bistable mulltivibrators 272, 274, 276 and 278, respectively.

In addition to being connected to the grid of the left tube in the multivibrator 278, the output terminal of the gate circuit 266 is also connected to the grid of the left tube -in a bistable multivibrator 288 and to the grid of the right tube in a bistable multivibrator 282. Similarly, the output from the gate circuit 268 is introduced to the grid of the right tube in the multivibrator 280 and the grid of the left tube in the multivibrator 282.

Connections are made from the output terminal of the gate circuit 268 through an or network 283 to an or network 284, to the grid of the left tube in a `bistable multivibrator 292, directly to the grid of the left tube in the bistable `multivibrator 286, and to the grids of the right tubes in bistable multivibrator 288 and 29). The output terminal in the gate circuit 266 is connected through an or network 291 to the or network 284, to the grid of the left tube in the multivibrator 292, directly to the grid of the riglrt tube in the multivibrator 286, and to the grids of the left tubes in the multivibrators 288 and 290.

The plates of the two tubes in each ofthe multivibrators 292, 286, 288 and 290 are connected to an adder 296. Only certain of these connections are shown for purposes of convenience. The adder 296 also receives the signals from the plates of the two tubes in the multivibrators 272, 274, 276 and 278 and arithmetically combines this information with the signals from the multivibrators 2.92,

286, 288 and 298. The adder 296 isa four-digit parallel binary adder. One form of such an adder is shown and described on page 4l or a book entitled Automatic Digital Calculators by Booth and Booth, published in 1953 by Butterworth Scientiiic Publications, London. The adder shown therein functions to combine in a parallel manner, binary-coded values registered in two registers. Similarly, the adder 296 functions to additively combine (in a parallel manner), the value registered in the multivibrators 292, 286, 288 and 298 with the value registered in the multivibrators 272, 274, 276 and 278. The results obtained are introduced to the appropriate grids of the two tubes in each of bistable multivibrators 388, 382, 304 and 386. Only certain of the connections to the multivibrators 380, 302, 384 and 306 are shown for purposes of convenience.

As shown in FIGURE 3, the voltages on the plates of both tubes in the multivibrators 282, 286, 218 and 214 are connected to input terminals of gate circuits such as gate circuits 310, 312, 314 and 316. For purposes or simplicity, only the gate circuits 318, 312, 314 and 316 are shown in FIGURE 3. Other terminals of the gate circuits such as the circuits 318, v312, 314 and 316 are connected to the plate of the left tube in a multivibrator 318 corresponding to the multivibrator 98 shown in FIGURE l to receive the start pulses. The grid of the left tube in the multivibrator 318 receives its voltage from the output terminal of a gate circuit 328 cor-responding to the gate circuit 94 shown in FIGURE l. 4Input terminals of the gate circuit 320 are connected to the plate of the left tube in the multivibrator 286 and through a line 322 to the counter 234.

The output signals from the gate circuits such as the gate circuits 318, 312, 314 and 316 are introduced to delay lines such as the delay lines 325, 326, 327 and 328 for a delay of one pulse position. These delay lines may be bistable multivibrators similar to those disclosed above. The output signals from the gate circuits such as the circuits 310, 312, 314 and 316 and from the delay lines such as the lines 325, 326, 327 and 328 are introduced to an adder 324. The operation of the adder 324 is controlled by the voltage on the plate of the lefit tube in the multivibrator 318 and by sign-als passing through gate circuits 329 and 338.

In addition to being connected to one of the gate circuits corresponding to the circuits 318, 312, 314 and 316, the plate of the left tube in the multivibrator 218 is connected to input terminals of gate circuits 331, 332 and 334. Connections are made to other input terminals of the gate circuit 331 from the plate of the left tube in the multivibrator 218 and through the line 232 from the counter 234. The signals passing through the gate circuit 331 are applied to the grid of the left tube in a multivibrator 338, the grid of the right tube in the multivibrator being connected through a line 348 to the counter 234.

Like the gate circuit 331, the gate circuits 332 and 334 receive voltages through the line 232 from the counter 234. voltages are also respectively applied to input terminals of the gate circuits 332 and 334 from the plates of the left and right -tubes in the multivibrator 222. The output signals from the gate circuit 332 pass to the grid of the left tube in a bistable multivibrator 358, and the output signals from the gate circuit 334 pass through an or network 351 to the grid of the right tube in the multivibrator. Signals from the counter 234 also pass through the line 346 and the or network 351 to the grid of the right tube in the multivibrator 358. The voltages on the plates of the left and right tubes in the multivibrator 35) are in turn respectively applied to gate circuits 352 land 354 having other input terminals connected to the plate of the left tube in the multivibrator 338.

The output signals from the gate circuits 352 and 354 are respectively connected to input terminals of the gate circuits 329 and 33t), other input terminals of which are connected to the plate of the right tube in a multivibrator 1 5 358. The grid of the right tube in the multivibrator 358 is connected to an output terminal of an or network 360, input terminals of which are connected to a gate circuit 362 and through the line 340 Ato the `Counter 234. Connections are made to input terminals of the gate circuit 362 from the coil 62 in the channel 26 and from the plates of the left tubes in the multivibrators 318 and 358.

The voltage on the plate of the right tube in the multivibrator 358 is also applied to an input terminal of a gate circuit 364. Other input terminals of the gate circuit 364 are connected to the coil 62 and to the plate of the left tube in the multivibrator 318, and the output terminal is connected to the grid of the left tube in the multivibrator 358. In addition, the voltage on the plate of the right tube in the multivibrator 358 is applied to an input terminal of a gate circuit 366, another input terminal of which is connected to the plate of the right tube in the multivibrator 338. The signals passing through the gate circuit 366 are introduced to an or network 368 having its output terminal connected to the grids of the left tubes in the multivibrators 300 and 302 and to the grids of the right tubes in the multivibrators 304 and 306.

Connections are made from the plate of the left tube in the multivibrator 358 to input terminals of gate circuits 370 and 372. The gate circuit 370 has `a second input terminal connected to the plate of the lett tube in the multivibrator 280 and the gate circuit 372 has a second input terminal connected to the plate of the right tube in the multivibrator. The output from the gate circuit 3'72 is applied to lthe or network 368, and the output from the gate circuit 370 is introduced to the grids of the right tubes in the multivibrators 300 and 302 and to the grids of the left tubes in the multivibrators 304 and 306.

The output from the adder 324 shown in FIGURE 3 is applied to the grids of both tubes in each of the multivibrators 272, 274, 276 yand 278 shown in FIGURES 2 and 4. lOnly certain of these connections are shown for purposes of convenience. The output from the adder 324 is also applied to gate circuits 376 (FIGURE 4) and 378 having other input terminals connected to the plate of the left tube in the multivibrator 318. The output signals from the gate circuits 376 and 378 are in turn respectively introduced to the or ne-tworks 283 and 291 also shown in FIGURE 2. As previously disclosed, the signals passing through the or network 283 and 291 control the operation of the multivibrators 292, 286, 288 and 290.

The output signals passing through the gate circuits 376 and 378 are also respectively introduced to the grids of the left and right tubes in the bistable multivibrator 282 also shown in FIGURE 2. Connections are respectively made from the plates of the left and right tubes in the multivibrator 282 to input terminals of gate circuits 382 and 384, each of which has another input terminal connected to the plate of the left tube in a multivibrator 386.

The grid of the left tube in the multivibrator 386 receives signals from an output terminal of a gate circuit 388 having input terminals connected to the coil 62 in the channel 26 and to the plate of the left tube in the multivibrator 318. The grid of the right tube in the multivibrator 386 has a voltage introduced to it through a line 390 from the counter 234, and the plate of the right tube in the multivibrator has its voltage applied to a gate circuit 392. Other input terminals of the gate circuit 392 are connected to the coil 62 and to the plate of the left tube in the multivibrator 318. The output from the gate circuit 392 passes to the coil 36 through the or network 245 also shown in FIGURE 2.

The output signals from the gate circuits 382 and 384 are respectively introduced to the grids of the left and rightY tubes in a multivibrator 393. As shown in FIG- URES 3 and 4, the voltages on the plates of the left and right tubes in the multivibrator 393 -are introduced to the adder 324 for combination with the signals from the multivibrators 300, 302, 304 and 306 and the signals from the gate circuits corresponding to the circuits 312, 314, 316 and 318. As will be disclosed in detail hereinafter, the voltages on the plates of the two tubes in the multivibrator 393 control the carry to one pulse position of the results obtained by the addition in the adder 324 of information provided for a previous pulse position.

As shown in FIGURE 2 and disclosed previously, the output from the multivibrators 272, 274, 276 and 278 is combined in the adder 296 with the output from the multivibrators 292, 286, 288 and 290. The particular pattern of voltages introduced to the adder 296 from the multivibrators 292, 286, 288 and 290 is controlled by the voltages from the gate circuits 266 and 268. The connections to obtain the particular patterns of voltages in the multivibrators 292, 286, 288 and 290 for a high voltage on the output terminals of either the gate circuit 266 or the gate circuit 268 are shown in FIGURE 2 and have been disclosed previously.

The output signals from the adder 296 are applied to gate circuits such as the circuits 394, 395, 396 and 397 in FIGURE 4. Other input terminals of the gate circuits corresponding to the circuits 394, 395, 396 and 397 are connected to the plate of the left tube in the multivibrator 386, and the output terminals of the gate circuits are connected to the grid of one of the tubes in the multivibrators 244 and 250 and in multivibrators 398 and 399.

As shown in FIGURE 5, the voltages on the plates of the left tubes in the multivibrators 206 and 210 are respectively introduced to input terminals of gate circuits 400 and 402. The gate circuits 400 and 402 also receive signals through the line 340 from the counter 234 and introduce their output signals to the grids of the left tubes in bistable multivibrators 404 and 406. The grids of the right tubes in the multivibrators 404 and 406 are connected through the line 390 to the counter 234.

Connections are made from the plate of the left tube in the multivibrator 404 to input terminals of gate circuits 408 and 410 and from the plate of the right tube in the multivibrator 404 to input terminals of gate circuits 412 and 414. The gate circuits 408 and 412 also receive the output signals from a gate circuit 416 having its input terminals connected to the plate of the right tube in the multivibrator 406 and through the line 340 to the counter 234. Other input terminals of the gate circuits 408 and 412 are respectively connected to the plates of the right and left tubes in the multivibrator 350, which is also shown in FIGURE 3. The output signals from the gate circuits 408 and 412 pass through or networks 420 and 422 to the coil 58 for recordation in the channel 24.

Other input terminals of the gate circuits 410 and 414 have voltages applied to them from a gate circuit 424, which in turn has input terminals connected to the plate of the left tube in the multivibrator 406 and through the line 340 to the counter 234. The gate circuits 410 and 414 also have input terminals respectively connected to the plates of the left and right tubes in the multivibrator 350. The output signals from the gate circuits 410 and 414 pass through the or networks 420 and 422 to the coil 58 for recordation in the channel 24.

Connections are made to a gate circuit 428 from the plates of the left tubes in the multivibrators 282 and 338 and through the line 340 from the counter 234. The output signals from the gate circuit 428 are applied to input terminals of gate circuits 430 and 432. Other input terminals of the gate circuit 430 are connected to the plate of the left tube in the multivibrator 350 and to the plate of the right tube in the multivibrator 404. In like manner, other input terminals of the gate circuit 432 are connected to the plate of the right tube in the multivibrator 350 and the plate of the left tube in the multi- VbratOr 404, The output signals from the gate circuits 17 430 and 432 pass through or networks 434 and 436 to the coil 52 for recordation in the channel 22.

Signals are applied to a gate circuit 438 from the plate of the left tube in the multivibrator 338, from the plate of the right tube in the multivibrator 282and through the line 340` from the counter 234. The output signals from the gate circuit 438 passv to input terl'ninalsv of gate circuits 440 and 442. Other input terminals of the gate circuit 440 are connected to the plates of the left tubes in the multivibrators 350` and 404. Connections are alsoV made to other input terminals of the gate circuit 442 from the plates of the right tubes in the multivibrators 350` and 404. The output signals from the gate circuits 440 and 442 pass through the or networks 434 and 436 to the coil 52 for recordation in the channel 22.

The signals from a pair of gate circuits 444 and 446 also pass through the or networks 436 and 422 for recordation by the coils 52 and 58 in the channels 22 and 24, respectively. Input terminals of the gate circuit 444 are connected to the plate of the left tube in the multivibrator 218 and through a line 448 to the counter 234. Similarly, connections are made to input terminals of the gate circuit 446 from the plate of the left tube in the multivibrator 222 and through the line 448 from the counter 234.

ln FIGURE 6, a plurality of gate circuits 450, 452 and 454 are connected in various arrangements to the multivibrators 280, 393 and 404. Connections are made to input terminals of the gate circuit 450 from the plate of the left tube in the multivibrator 280, from the plates of the right tubes in the multivibrators 393 and 404 and through the line 340 from the counter 234. Voltages are applied to input terminals of the gate circuit 452 from the line 340, the plate of the left tube in the multivibrator 404 and the plates of the right tubes in the multivibrators' 2850 and 393. Similarly, signals pass to input terminals of the gate circuit 454 from the line 340 and the plates of the left tubes in the multivibrators 280, 393 and 404. The output signals from the gate circuits 450, 4'52 and 454 pass through an or network 456 to thev grid of the left tube in the multivibrator 276, which is also shown in FIGURE 2.

Signals from the multivibrators 280, 393 and 404 are also applied to gate circuits 460, 462 and 464 in particular arrangements. The gate circuit 460 receives signals Vfrom the plates of the left tubes in the multivibrators 393 and 404, from the plate of the right tube in the multivibrator 280 and through the line 340 from the counter 234. Voltages are applied to input terminals of the gate circuit 462 from the line 340 and the plates of the right tubes in the multivibrators 280, 393 and 404. Connections are made to input terminals of the gate circuit 464 from the line 340', from the plates or the left tubes in the multivibrators 280 and 3593 and from the plate of the' right tube in the multivibrator 404. The output signals from the gate circuits 460, 462, and 464 pass through an or network 466 to the grid of the right tube in the multivibrator 276.

As previously disclosed, a pulse is provided in the channel 18 in one of the rst 22 positions for each integrator to Control the occurrence of a Ax increment for the integrator every time that the integrator is presented for Computation. The particular position in which the coding pulse is recorded for the integrator undergoing computation is dependent upon which of the other integrators feeds Ax increments into the integrator undergoing computation. Since the connections between integrators remains constant during the solution of a problem, the coding pulse in the channel 18 in one of the rst 22 positions for each integrator remains constant during the solution of the problem. As a result, these pulses have to be retained during the solution of a problem.

Retention of the pulses in the channel 178 is provided by the multivibrator 210 (FIGURE 2), the gate circuits to the coil 42 for 23.6 and 238 and stages associated with these gate circuits. The pulses in the channel It3 having a first polarity of magnetization are converted by the coil 38 to pulses of relatively high voltage. These voltage pulses `are then introduced to the grid of the left tube in the multivibrator 210 so as to cut orf the tube. When the left tube in the multivibrator 210 becomes cut oi, a high voltage is produced on the plate of the tube and is introduced to the gate circuit 236.

The gate circuit 236 is opened by a signal from the counter 234 when the iirst pulse in each integrator is picked upby Ithe coil 62. The gate circuit 236 remains open so that information in the channel liti up to and including the 22nd pulse position for each integrator can pass through the gate circuit. During the time that the gate circuit 236 remains open, the positive pulses from the plate of the left tube in the multivibrator 210 pass through the gate circuit to the or network 246. The network 246 in turn passes to the grid of the left tube in the multivibrator 250 any positive pulses introduced to it. These signals cause the left tube in the multivibrator 250 to become cut oir land a positive pulse of voltage to be produced on the plate. The positive voltage pulse passes recordation in the channel 18. In this Way, the coil 42 operates to produce a magnetic field in the channel 18 similar to the pattern of the electrical signals induced in the coil 38.

In like manner, a pulse of low voltage is induced in the coil 38 to indicate the integer 0 for a pulse position. This voltage pulse is inverted by the inverter 212 and introduced as a positive pulse to the grid of the right tube in the multivibrator 210 to cut off the tube and to produce a positive pulse on the plate of the tube. When such a pulse is produced in one of the first 22 positions for an integrator, the gate circuit 233 opens and the pulse passes through the gate circuit and the or network 243 to the grid of the right tube in the mutivibrator 250. Since the right tube in the multivibrator becomes cut off upon the introduction of such a pulse, the left tube becomes conductive. This causes a pulse of low voltage to pass to the coil 42 for recordation in the channel 18.

Similarly, the multivibrator 206, the gate circuit 2218, the or network 240 and the multivibrator 244 in FlG- URE 2 operate lto recirculate in the channel 16 the posi- -tive coding information provided in the first 22 positions of each integrator. As previously disclosed, positive pulses may be provided in the channel 16 in the rst 22 positions yfor each integrator to indicate whether any variations in the value of the dependent quantity y will be made for the integrator.

The gate circuit 254 operates Ato determine whether or not an actual Ay increment is made for an integrator at the time that a coding pulse appears in the channel 16 in one of the rst 22 positions for the integrator. The gate circuit 254 receives the coding pulses in the channel 16 because of its connection to the plate of the left tube in the multivibrator 206. The connection from the counter 234 through the line 232 to the gate circuit 254 causes the gate circuit to become open during the first 22 positions of each integrator. The operation of the counter 234 to provide -a relatively high voltage during the iirst 22 positions of each integrator is fully disclosed in copending application Serial No. 217,478, tiled March 26, 1951, by Steele and Collison.

Since the gate circuit 254 is also connected to the plate of the left tube in the multivibrator 218, it can open for the passage of a signal only when high voltages are simultaneously produced on the plates of the left tubes in the multivibrators 206 and 218. A relatively high Voltage is produced on the plate of the left tube in the multivibrator 21S only when a relatively high voltage is induced in the coil 54. As previously disclosed, the -coil 54 indicates in adjacent pulse positions any overow in the value of the cumulative yAx increments which are obtained for each of the 22 integrators in the analyzer. 

